The aircraft, an E-6B Mercury, was being moved at Tinker Air Force Base in Oklahoma during regular operations when the vertical stabilizer (a flattened projecting attachment on an aircraft that provides aerodynamic stability) at the aircraft's rear clipped the hangar, Lt. Travis Callaghan, a spokesperson for the Naval Air Forces, told military.com.
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One person was inside the aircraft during the accident, as it is standard procedure to have a "brake rider" on board the aircraft whenever it is being towed out of a hangar, Callaghan added.
Photos of the incident shared on social media show the vertical stabilizer broken away from the plane.
According to the Naval Safety Center, the incident has been labeled a Class-A mishap, which is defined as an incident that costs $2 million or more to repair. The accident is under investigation, after which decisions will be made "as to what repairs are required and a way ahead for the aircraft," Callaghan noted.
The E-6B Mercury, a Boeing 707 commercial plane, is part of the Navy's "Take Charge and Move Out" mission.
The plane is tasked with carrying survivable communications links to be used in nuclear warfare to ensure communications between the National Command Authority and strategic nuclear weapon delivery system including US submarine, bombers and missile silos. The National Command Center refers to the president of the US and the Secretary of Defense jointly.
According to Naval Safety Center data, this incident is the Navy's fifth Class-A aviation mishap in the last five months. The average number of mishaps between fiscal years 2009 and 2018 is around 12.